package leetcode;

/*
用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。(若队列中没有元素，deleteHead 操作返回 -1 )
示例 1：
输入：
["CQueue","appendTail","deleteHead","deleteHead"]
[[],[3],[],[]]
输出：[null,null,3,-1]
示例 2：
输入：
["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
[[],[],[5],[2],[],[]]
输出：[null,-1,null,null,5,2]
提示：
1 <= values <= 10000
最多会对 appendTail、deleteHead 进行 10000 次调用
*/

import java.util.Stack;

public class Offer_009 {
    public static void main(String[] args) {
        CQueue queue = new CQueue();
        queue.deleteHead();
        queue.appendTail(5);
        queue.appendTail(2);
        queue.deleteHead();
        queue.deleteHead();
    }

    /***
     *
     */
    static class CQueue {
        private Stack<Integer> stackA;
        private Stack<Integer> stackB;
        public CQueue() {
            stackA = new Stack<>();
            stackB = new Stack<>();
        }
        public void appendTail(int value) {
            while (!stackB.isEmpty()){
                stackA.push(stackB.pop());
            }
            stackA.push(value);
            while (!stackA.isEmpty()){
                stackB.push(stackA.pop());
            }
        }
        public int deleteHead() {
            if (stackB.isEmpty()) return -1;
            return stackB.pop();
        }
    }
}

